The receptor for tetrahydrocannabinol (THC) is cannabinoid receptor 1 or 2 (cannabinoid receptor 1/2, called CB1 or CB2 for short). The discovery promotes scientists to study endogenic ligands of cannabinoid receptor. It has been found now that N-arachidonoylethanolamine (anandamide, AEA), O-arachidonoylethanolamine (virodhamine), N-arachidonoyldopamine and the like are endocannabinoids acting on cannabinoid receptor. Like lipid transmitters such as prostaglandin, these endocannabinoids are synthesized in situ according to actual need rather than accumulated in vivo, are modulated by enzymes and receptors, and can be metabolized by the specific hydrolases into the corresponding substances such as fatty acid, ethanolamine and glycerol, thereby reducing their effects in vivo.
AEA is the first found endocannabinoid (Devane W A, Hanus L, Breuer A, et al., Science, 1992, 258:1946-1949; Di Marzo V, De Petrocellis L., Curr Med Chem, 2010, 17:1430-1449; Gasperi V, Dainese E, Oddi S, et al., Curr Med Chem, 2013, 20:64-78.), mainly activates CB1 receptor, and can have pharmacological functions similar to those of Cannador such as THC. AEA is widely distributed in vivo, and is detectable in central nervous system, and organs such as liver, lung and gastrointestinal tract. AEA can have pharmacological actions such as anti-inflammatory effect and analgesic effect by direct activation of endocannabinoid receptor (CB). In addition, it has been reported that AEA also has relatively weak agonistic effects on transient receptor potential cation channel subfamily V member 1 (TRPVI) (Bouaboula M, Hilairet S, Marchand J, et al., Eur J Pharmacol, 2005, 517:174-181; Mechoulam R, Ben-Shabat S, Hanus L, et al., Biochem Pharmacol, 1995, 50:83-90; Sugiura T, Kondo S, Sukagawa A, et al., Biochem Biophys Res Commun, 1995, 215:89-97.), G protein coupled receptor 55 (GPR55) (Sugiura T, Waku K., Journal of Biochemistry, 2002, 132:7-12; Sigel E, Baur R, Racz I, et al., Proc Natl Acad Sci USA, 2011, 108:18150-18155; Guindon J, Hohmann A G., Cns & Neurological Disorders-Drug Targets, 2009, 8:403-421; Nomura D K, Long J Z, Niessen S, et al., Cell, 2010, 140:49-61; Fowler C J, Gustafsson S B, Chung S C, et al., Current Topics in Medicinal Chemistry, 2010, 10:814-827.), and peroxisome proliferator-activated receptor γ (PPAR-γ) (Arevalo-Martin A, Garcia-Ovejero D, Molina-Holgado E., Neurobiology of Disease, 2010, 38:304-312; Scotter E L, Abood M E, Glass M., British Journal of Pharmacology, 2010, 160:480-498; Cobellis G, Ricci G, Cacciola G, et al., Biology of Reproduction, 2010, 82:451-458; Guida M, Ligresti A, De Filippis D, et al., Endocrinology, 2010, 151:921-928.). AEA is one of the endocannabinoids widely studied now, and AEA is regarded as partial agonist of cannabinoid receptor.
Besides, some fatty acyl ethanolamine lipids, such as N-Oleoylethanolamide (OEA) and N-palmitoylethanolamide (PEA), which do not act on cannabinoid receptor directly, but have similar structures and similar functions in terms of endocrine regulation as AEA and 2-AG (2-arachidonoylglycerol), are called endocannabinoid-like substances. PEA and OEA act on peroxisome proliferator-activated receptor α (PPAR-α) to generate analgesic and anti-inflammatory effects and appetite-suppressing effects (Fu J, Gaetani S, Oveisi F, et al., Nature, 2003, 425:90-93.). Particularly, PEA is widely distributed in vivo, and PEA can act on multiple targets such as central and sensory nervous system, and immunocyte to show analgesic and anti-inflammatory effect. PEA can activate nuclear receptor peroxisome proliferator-activated receptor-α (PPAR-α), or partially activate GPG55 receptor and GPR119 receptor to generate multiple pharmacological actions such as anti-inflammatory effect and analgesic effect (Mol Pharmacol, 2005, 67, 15-19). N-stearoylethanolamine (SEA) can promote apoptosis of tumor cells (Maccarrone M, Pauselli R, Di Rienzo M, et al., Biochem J, 2002, 366:137-144) and suppress appetite (Terrazzino S, Berto F, Dalle Carbonare M, et al., FASEB J, 2004, 18:1580-1582); Oleamide (OA) has the effects such as sleep regulation (Huitron-Resendiz S, Gombart L, Cravatt B F, et al., Exp Neurol, 2001, 172:235-243).
AEA can be hydrolyzed to arachidonic acid and ethanolamine by specific fatty acid amide hydrolase (FAAH), and therefore lose activity. FAAH, obtained by clone in 1996, belongs to amidase signature family, is the first protein of this family found in mammal and presents in intracellular membrane, and has a segment of transmembrane alpha helix. FAAH protein consists of 579 amino acids, and the crystal structure of FAAH has been obtained now. The active center of hydrolysis substrate AEA consists of typical Ser-Ser-Lys (Ser241-Ser217-Lys142). The optimal hydrolytic condition for FAAH is a slightly alkaline pH (pH=8˜9), and FAAH is highly selective for hydrolysis of AEA among fatty acid acyl ethanolamine substrate compounds. In addition, FAAH can also hydrolyze other fatty acid amides such as OEA, PEA, and OA (McKinney M K, Cravatt B F., Annu Rev Biochem, 2005, 74:411-432; Fezza F, De Simone C, Amadio D, et al., Subcell Biochem, 2008, 49:101-132), but with a relatively weak hydrolytic activity.
In FAAH gene-knockout mice, AEA level was significantly increased in central and peripheral tissues (Cravatt B F, Demarest K, Patricelli M P, et al., Proc Natl Acad Sci USA, 2001, 98:9371-9376). AEA level can also be significantly increased by inhibition of FAAH activity with small molecular compounds, however, animal exhibits cannabis-like side effects such as rigidity, reduced activity, and reduced body temperature. Now, FAAH inhibitors have certain effects against depression, anxiety, neuropathic pain and the like. Some FAAH inhibitors have been studied in clinic for the treatment of depression, arthritis pain and the like. FAAH inhibitors can be divided into the following four classes depending on their structures: early AEA substrate analogs, α-ketone heterocyclic compounds, carbamates and aromatic ureas.
The specific hydrolase for PEA, N-acylethanolamine acid amidase (NAAA), had not been found and cloned until 2005 (Tsuboi K, Sun Y X, Okamoto Y, et al., J Biol Chem, 2005, 280:11082-11092). Natuo Ueda research group found a cannabinoid hydrolase with the activity of hydrolyzing AEA in a human megakaryoblastic cell line (CMK) in 1999 (Ueda N, Yamanaka K, Terasawa Y, et al., FEBS Lett, 1999, 454:267-270). However, the enzyme is quite different from the known AEA hydrolase FAAH in the following aspects: (1) the enzyme has a high hydrolytic activity at acidic pH (pH 4.5), while FAAH enzyme has a high hydrolytic activity at basic condition (pH 9.0) (Linsenbardt D N, Boehm S L, 2nd., Neuroscience, 2009, 164:424-434); (2) the enzyme is much more active for the hydrolysis of PEA than for hydrolysis of AEA; and (3) the enzyme is not sensitive to serine inhibitors PMSF and MAFP that have good inhibitory effect on FAAH. Soon after, the research group found that NAAA enzyme was most active in lung among various tissues, was less active gradually in tissues such as spleen, thymus gland and small intestine, and was finally purified in lung tissues (Ueda N, Yamanaka K, Yamamoto S., J Biol Chem, 2001, 276:35552-35557). In 2005, the cDNA sequence of the enzyme was cloned from rat, mouse and human-derived cells, and the enzyme was denominated as N-Acylethanolamine-hydrolyzing Acid Amidase (NAAA) (Tsuboi K, Sun Y X, Okamoto Y, et al., J Biol Chem, 2005, 280:11082-11092). It was found in a subsequent research that NAAA was mainly expressed in lysosomes (Tsuboi K, Zhao L Y, Okamoto Y, et al., Biochim Biophys Acta, 2007, 1771:623-632). NAAA comprises 362 amino acid residues in rat and mouse with a molecular weight of 40.3 Kda (rat) and 40.1 kDa (mouse) respectively, and it also comprises 359 amino acid residues in human) with a molecular weight of 40.1 kDa. Among these amino acid sequences, rat NAAA is 90.1% identical to mouse NAAA, rat NAAA is 76.5% identical to human NAAA, and mouse NAAA is 76.7% identical to human NAAA. Human NAAA gene is on 4q21.1 chromosome. NAAA, which has no homology with FAAH but has a certain homology with acid ceramidases, is classified into choloylglycine hydrolase family, and is selective for hydrolysis of amide (Tsuboi K, Sun Y X, Okamoto Y, et al., J Biol Chem, 2005, 280:11082-11092).
Due to lack of crystal structure, the steric configuration for hydrolysis-catalyzing domain of NAAA is not clear yet, and there are few specific inhibitors. Limited researches show that topical administration of β-lactam type NAAA inhibitor S-OOPP (IC50=420 nM) can inhibit the carrageenan-induced reduction in granulomatous leukocyte PEA content in rat as well as the LPS-induced reduction in cellular PEA content in RAW264.7, thereby inhibiting leukocyte migration and inflammatory exudation, and can also have good therapeutic effects in spinal injury model, the process was mediated by PPAR-α pathway (Solorzano C, Zhu C, Battista N, et al., Proc Natl Acad Sci USA, 2009, 106:20966-20971). Topical administration of a structural analog ARN077 (IC50=127 nM) can significantly inhibit inflammatory pain induced by carrageenan and neuropathic pain caused by sciatic nerve ligation. In sciatic nerve ligation models, ARN077 (1%, 20 μL, epidermal administration) has better analgesic effects on allodynia than the positive control agent gabapentin (50 mg/kg, oral administration) (Sasso O, Moreno-Sanz G, Martucci C, et al., Pain, 2013, 154:350-360). This research demonstrated for the first time that NAAA inhibitors have analgesic effects, the main pharmacophore 4-membered lactone ring for this class of structures is unstable structurally and has poor biological stability, with a half-life of less than 1 min in animal, and thus cannot be applied by systemic administration.
Compared to the analgesics such as opioids, anti-epileptics, anti-depressive agents and local anaesthetics, endocannabinoid hydrolase inhibitors have less side effects on central nervous system, and have no addiction; compared to COX inhibitors as anti-inflammatory analgesics, such as ibuprofen, celecoxib and aspirin, endocannabinoid hydrolase inhibitors have better drug safety as they would not result in intestine and stomach bleeding and serious cardiovascular event (Biochem J, 2004, 380, 749-756; Journal of Medicinal Chemistry, 2008, 51, 7327-7343; PAIN, 2013, 154, 326-327).
The object of the invention is to provide a novel, more stable endocannabinoid hydrolase inhibitor, and a preparation method and a use thereof.